The invention relates generally to gas filtration and the removal of compounds from gases using particulate matter, and more particularly to a frame or other structure for retaining particulate matter through which the gas is forced to reduce and/or remove compounds from the gas without the gas bypassing the particulate through large gaps between the particulate and the frame.
Filters are commonly produced that contain granular, pelletized, or particulate media that are designed to remove Volatile Organic Compounds (VOCs), odors or any other air-born contaminants that cannot be removed by mechanical or electrostatic filtration methods. As shown in FIGS. 1 and 2, these conventional filters may be made of a corrugated paper product frame with pockets or “cells” that contain the filtration medium particulate 8. The filter 1 may be made using an injection molded plastic frame that holds the particulate in multiple cells. Upper wall 2, lower wall 3 and lateral walls 4 define each of the cells and the walls 2-4 retain a quantity of filtration medium particulate 8 between upstream and downstream mounted, gas-permeable media 5 and 6 (see FIG. 2) that contain the particles of the particulate 8 that are larger than the pores in the media. The air, gas or liquid passing through the particulate follows a path that is perpendicular to the planar major face of the filter.
The particulate is sometimes referred to herein as “carbon” because carbon is the most common material used for this filtration purpose. Air that has greater contact with the carbon is more desirable because carbon removes more odors and VOCs from the airstream in a given time frame than many other such particles. Granular carbon is commonly used in such filters to capture odors and VOCs from air as the air is forced through a particulate bed. As described above, conventional granular or pelletized carbon filters employ a carrier system which typically includes multiple sidewall baffles that are aligned substantially parallel to the air stream, which is substantially perpendicular to the upstream media 5. The baffles, which are the walls 2-4, distribute the carbon particulate across the entire volume of the filter and hold the carbon in place when the filter is placed in various orientations. The nature of the cells is that the faces of the upper and lower walls 2-3 that the particulate seats against and that define the cells 8 are substantially perpendicular to the planar face of the filter frames as shown in FIGS. 1 and 2. Stated differently, the angle A of FIG. 2 is conventionally about 90 degrees, and, to the inventor's knowledge, is always substantially perpendicular, which is between about 87 and about 93 degrees even taking manufacturing tolerances into consideration.
The most common orientation for such filters during use is vertical. Because of the force of gravity, within each baffle set, or cell, the carbon particulate may settle to the bottom of the cell. This leaves an open space S at the top of each cell where air can pass through without coming into contact with the carbon. The filtration medium is loaded into the cells of the filters when the main plane of each filter is in a horizontal orientation, but when the filters are in use they are in a substantially vertical orientation. The geometric nature of the cells allows the carbon to settle and create a visible void where substantial amounts of air can move through the filter without being forced to go through the carbon. This condition is called “bypass” within the filtration industry and is illustrated in FIG. 2 as the line “B”. The problem with bypass is that a substantial amount of gas can pass through the open space S of the filter without being affected by the carbon particles. This produces poor odor and VOC reduction results. Therefore, the need exists for a superior filter frame to reduce or prevent such bypass.